1. Field of the Invention
The present invention relates to an improvement in a wheel speed calculation method for brake control designed for calculating the wheel speed used for brake control at the calculation timing of a given period based on a pulse signal provided by shaping the waveform of a detection signal of a wheel speed sensor.
2. Description of the Related Art
The following art is already known, for example, in JP-A-2-44258, etc.: To obtain the wheel speed used for antilock brake control and traction control of a brake, switching can be performed between the state in which the wheel speed is calculated using both the rising and falling edges and the state in with the wheel speed is calculated using either the rising or falling edge depending on the greater-than or less-than relationship between the number of the rising edges and that of the falling edges of a pulse signal occurring at the calculation timing of a given period within the calculation period.
By the way, in the related art, the purpose of calculating the wheel speed using either the rising or falling edge is to avoid an increase in the load on software for performing calculation processing of the wheel speed. However, to calculate the wheel speed based on either the rising or falling edge, if an error occurs in a wheel speed sensor, a comparatively large error occurs in the calculation processing result of the wheel speed, resulting in degradation of the brake control accuracy